I propose to analyze developmental programs by probing the action of juvenile hormone (JH) in controlling insect metamorphosis. In particular studies onn cuticular proteins are defining the magnitude of JH's role as a status quo agent. Development of an organ culture system which will make the appropriate kinds of cuticle in response to JH and/or ecdysone is a necessary prelude to using inhibitors which misht mimic JH's action. Other projects include examining the possibility that JH acts as an anti-mitotic agent and that the nature of JH's action can be understood by examining temperature sensitive periods for characteristics also controlled by JH. These studies use Hyalophora cecropia, Oncopeltus fasciatus and Tenebrio molitor.